I had an ancient friend that's long gone now that shot different colors of paint on all of his small wrenches and 1/4 drive sockets that matched the old standard nut driver color scheme. Red for 1/4, yellow for 5/16, green for 11/32, etc.
I asked him what kind of easy to memorize color scheme he was going to use on the larger size sockets. He told me that he wasn't, he could see still see those!